Drafting instrument.



PATENTED DEC. 19, 1905.

R. MARX.

DRAPTING INSTRUMENT.

APPLICATION FILED DEG. a, 1904 RICHARD MARX, OF PHILADELPHIA, PENNSYLVANIA.

DRAFTING INSTRUMENT.

Specification of Letters Patent.

Patented Dec. 19, 1905.

Application filed December 3, 1904. Serial No. 235,325.

To wZZ whom it may concern:

Be it known that I, RICHARD MARX, acitizen of the United States, residing in Philadelphia,

Pennsylvania, have invented certain Improvements in Drafting Instruments, of which the following is a specification.

My invention consists of a novel device or instrument for quickly finding and marking the center points from which to describe a circular arc to form a fillet or corner, as the case may be, in a drawing of any structure while this is being laid out or designed by a draftsman.

One object of my invention is to provide a conveniently-portable instrument by which the center from which any desired arc to be described may be quickly found by applying the instrument to the drawing and properly manipulating the same so as to form a mark or hole, in which one leg of apen-compass may be placed in order to describe an arc which will be tangent to the lines which it is desired to join by said are. The device may also be employed directly as a guide, by which circular or other curves may be conveniently drawn. These objects I attain as hereinafter set forth, reference being had to the accompanying drawings, in which Figure 1 is a plan view of the preferred form of my invention. Fig. 2 is a sectional elevation taken on the line 2 2 of the instrument shown in Fig. 1. Fig. 3 is a form of the instrument shown in Fig. 1, in which, however, the specially-formed recesses for drawing corners are omitted. Fig. 4 is a special form of the device shown in Fig. 1; and Fig. 5 is a sectional elevation of the instrument shown in Fig. 4:, the same being taken on the line 5 5 of said figure.

In designing machinery of various kinds it is frequently necessary where two surfaces intersect each other to draw a fillet or to show in a drawing the lines indicating two surfaces as each tangent to a circular arc. It is customary in practice when actually drawing this are to set a compass at the radius desired and to finally draw the arc tangent to the two lines from a center which is found only after a number of trials. By means of the instrument hereinafter described I am enabled to quickly find and mark with certainty the correct cen ter for an arc of any radiuswithin the usual limits, after which a compass set at the proper radius may be used to draw the are without further delay or trial.

Referring to Figs. 1 to 3 of the above drawings, A represents a relatively thin piece of sheet material having a series of projections or lobes extending from its periphery and indicated at a a, &c., each so made that a portion of its periphery is formed as a circular are. For example, the outer edge of the projection a is formed or cut to a radius of onehalf an inch. The various projecting lobes are preferably so arranged that they successively and progressively decrease in size-c. g., while the projection a is formed with a radius of half an inch the projection a has aradius of seven-sixteenths of an inch, the projection a has a radius of three-eighths, and so on.

For convenience, however, I indicate not the radius, but the diameter, of each of the lobes by properly stamping or marking the sheet A, as indicated.

The body or piece of sheet material may be recessed between adjacent projections, as shown at b 6 6 ($20., each of the recesses being formed on a different radius and the various recesses being of such dimensions that their radii vary progressivelyth at is to say, the recess Z) is formed on a radius of seven thirty-seconds of an inch and the recess 6 on a one-fourth-inch radius, and so on.

In order to mark the center points from which the arcs of the various projections may be described, I provide an arm C, pivotally mounted at the center of the body-piece A by means of a rivet c. Said body-piece is preferably pressed up to provide a recess for the lower head of the rivet, as indicated at a and the arm G is thereby elevated at its pivoted end above the general surface of the said body-piece. Said arm is of spring material and has a projection or pin 0 near its outer end formed to enter any one of a number of holes 0 formed in the body-piece A,

it being noted that these various openings or recesses are so placed that when the arm is held immovable by reason of the entrance of the pin 0 in one of said recesses a center point 0 carried by the extreme end of said arm, is in a line joining the center of the pivot c with the center from which one of the arcs of a projection a or a recess 6 is described.

It will be seen that the end of the arm C is so bent or formed as to normally retain the center point 0 slightly above the level of the upper surface of the body piece or plate A, it being therefore possible to freely move the arm C to any point upon the plate without injury to said point. At the center of each of the various projections a (0, &c., is a relaof-an-inch radius, to connect two lines at sub-- stantially right angles to each other, the arm 0 is turned on its pivot until its pin 0 enters the hole or recess 0 opposite the projection marked t. The instrument is then manipulated so that the curved edge of the projection a is tangent to both of the lines between which it is desired to draw the curve representing the fillet, and when this condition is attained the pointer end of the arm 0 is depressed so that the pointer 0 passes through the small opening a and makes a hole or mark on the drawing-paper.- A compass set to the radius of one-fourth of an inch is now used to describe the arc finally joining the two lines. Similarly, if it be desired to find the center from which any of the recesses b I), &c., may be described the edges of the recess of the proper size are placed tangent to the two lines between which ity is desired to draw a circular curve and the end of the arm 0 is depressed so as to mark the center from which the desired curve may finally be drawn.

If desired, the circular recesses may be omitted between the various projecting lobes a a, &c., the various ends of said lobes being then separated from one another by a portion of the edge of the plate A, formed as part on a circular are described from the center of the pivot 0.

While in Figs. 1 to 8, inclusive, 1 have shown my invention as applied to a plate of substantially circular form, it will be understood that, if desired, it may be'shaped, as shown in Figs. 4: and'5, as an elongated plate having the various projecting portions a a, &c., extending from its two longitudinal edges. In this case, however, the arm carrying the center point 0 would be provided with a guideway c4 preferably pressed up from the body of the plate, as shown in Fig. 5, upon which the arm 0 could be made to slide in any desired position, so as to be available for use, as described in connection with that form of the device shown in Figs. 1 to 3.

Inasmuch as the various recesses and projections are of exact sizes, it will be understood that in making pencil-drawings these curves may be used directly in putting in fillets, corners, &c., while when it is desired to ink in the drawing the arm C, carrying the center point, is depressed at each fillet, &c., so as to make a small hole in the drawing-sheet, which may be used as the center for one leg of a pencompass.

I claim as my invention 1. A'drafting instrument including a plate having a series of projections of curved outlines, with a device movably mounted on the plate for marking the centers of the curves defining said outlines, said device having guidlines, there being a recess also of curved out' line between each pair of adjacent projections, a device movably mounted on the plate for marking the centers of the curves defining said outlines, and guiding means for said device whereby it is maintained in proper position relatively to the line connecting said centers, substantially as described.

3. A drafting instrument including a plate having a series of substantially semicircular lobes, and openings coincident with the centers of the curves defining said lobes, with a device adjustably connected to the plate operative through said openings for marking said centers of'the curves, substantially as described.

4. A drafting instrument including a plate having a series of circularly-curved lobes of diiferent radii, there being openings in the plate coincident with the centers of the arcs defining said lobes, and means guided on the plate for marking the positions of said openings, substantially as described.

5. A drafting instrument including a plate having a series of substantially circularlycurved lobes, there being openings in the plate coincident with the centers of the curves of said lobes, and an arm movably connected to the plate having means for marking upon any desired surface the center of any of said lobes, said arm having guiding means for directing its motion relatively to the line of said openings, substantially as described.

6. The combination in a drafting instrument of a plate, and an arm movably mounted thereon, a series of projections of curved outlines extending from the edges of the plate, and a point carried by the arm for marking the centers of the curves defining said projections, said arm having means for guiding it relatively to the line of said centers, substantially as described.

7. The combination of a plate having its edge formed as a series of projections of substantially semicircular outline, there being openings in the plate substantially coincident with the centers of the various lobes, and an arm carrying a marking-point movable upon the plate, and means for retaining the arm in position with its point over any of the center openings of the projections, substantially as described.

8. A plate having a series of projecting-lobes of substantially semicircular form and each provided with a central opening, an arm having a point for marking the centers of the various lobes, said arm being movable so as to maintain said point in a line connecting said centers, with a pin on the arm, the-same coacting with a series of openings in the plate so placed as to hold the arm immovable whenever its point is over the center opening of one of the lobes, substantially as described.

9. In a drafting instrument the combination of a plate having a series of projecting lobes curved to have circular outline, each provided with a central opening, with a spring-arm carried by the plate and provided with a marking-point constructed to pass through the central openings of the various lobes, said arm being guided so as to maintain the markingpoint in the line of said opening, substantially as described.

10. The combination of a plate having a series of circularly-curved lobes and recesses between adjacent lobes, also curved on circular arcs, with an arm carrying a markingpoint, and means for mounting the arm upon the plate so that as it is moved, its markingpoint travels in a line connecting the centers of the various lobes and recesses, substantially as described.

11. A drafting instrument including a plate having a series of lobes curved on circular arcs and openings coincident with the centers of the curves of said lobes, with aspring-arm pivoted to said plate and provided with a marking-point so placed as to pass through the central openings of the lobes, substantially as described.

12. A drafting instrument including a plate having a series of lobes curved on circular arcs and openings coincident with the centers of the curves of said lobes, with a spring-arm pivoted to said plate and provided with a marking-point so placed as to pass through the central openings of the lobes, there being means for retaining said pivoted arm in such position that its marking-point will be over the central openings of the lobes, substantially as described.

13. A drafting instrument including a plate having a series of circularly-curved portions, the centers from which said curved portions are described being the same distance from a given point, substantially as described.

14:. A drafting instrument including a plate having a series of circularly-curved portions, the centers from which said curved portions are described being the same distance from a given point, with a movable arm having means for marking said centers, substantially as described.

15. A drafting instrument including a plate having a series of circularly-curved portions, the curves of said portions being described from different radii, with an arm provided with a center marking device and mounted on the plate so that said device may be moved in a line connecting the centers of said curves, substantially as described.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

RIOHARD MARX.

Witnesses:

WILLIAM E. BRADLEY, J os. H. KLEIN. 

